Modern archery is the result of extended development through many years as practitioners endeavored to produce the capability for launching arrows with greater and greater energy power range and accuracy. From earliest bows which, were in essence, simple resilient wooden members drawn into a curved position by a bowstring, archery bows have developed through the application of scientific endeavor into extremely high technology apparatus useful in sporting and hunting activities. While archery bows originally formed of resilient wood or other resilient material operated in a straight forward easily understood manner in which the resilience of the bow stored energy as the bowstring was drawn, modern archery bows operate in a much more complex and sophisticated manner. The result of this complex and sophisticated fabrication greatly increases the power and accuracy of the modern bow.
In its typical fabrication, the modern bow provides a rigid riser which supports a pair of limb sockets at its upper and lower ends together with a handle grip near the center. The riser typically supports an arrow rest structure which may be either static or movable as preferred. A pair of flexible resilient limbs are supported by each limb socket and extend rearwardly to define movable end portions. The movable ends of the flexible limbs support one or more rotatable cams. Each cam defines a profile which translates its rotational motion to the desired distance from the center of rotation to produce the camming action. In most modern archery bows, a pair of cables are strung over and between the cams to provide the “bowstring” for knocking the arrow. Because the cables typically pass between the cams several times, a cable guide apparatus is often provided which offsets the additional cable portions from the cable path of the main bowstring portion.
As the bowstring is drawn, the cables are drawn over the cams rotating the cams and flexing the limbs inwardly to store energy as the limbs are bent. The action of the cams influences the draw characteristics of the bow and the energy storage in the flexing limbs. With the arrow held against the bowstring portion of the cables and the bow drawn, the release of the cable allows the limbs to spring outwardly toward their original positions rapidly rotating the cams and drawing the cable back toward its original static position. The rapid movement of the bowstring portion of the cable transfers the energy of the stored limbs into the arrow and launches the arrow. The profiles of the cams are designed and selected to produce the force and acceleration characteristics of the bow to maximize the energy transferred to the arrow for a given draw strength.
The optimum performance of a modern archery bow requires that the cams be precisely positioned relative to each other throughout the rotational range of operation. In particular, the optimum performance of the archery bow requires that the cams be rotationally synchronized in their draw positions. The precision of rotational positions of the cams is required to ensure that the cams rotate together in synchronism when the bowstring is released. The object of cam positioning is to ensure that the bowstring when released moves forwardly without being drawn upwardly or downwardly. If the cams of the bow are not properly synchronized in their operation, the portion of the bowstring to which the arrow is knoched is moved vertically as well as forwardly. This vertical motion raises or lowers the end of the arrow as it is driven forward during launch. Vertical motion of the arrow in turn changes the angle of the arrow as it is driven forward leading to inaccurate launch and flight.
The critical need for proper synchronization of cam position and action in the modern archery bow leads to a process of fabrication and preparation typically referred to in the art as “timing”. Practitioners typically place the bow in a specialized fixture which supports the bow and applies force to the limbs flexing them inwardly to a position corresponding to the full draw of the bow. With the limbs flexed by the adjustment fixture, the practitioner then adjust the length of each cable to obtain identical rotational positions for each cam. In many instances, this cable length adjustment is carried forward by twisting either or both of the cables. While this method of cam timing can be accurate and effective while practiced by a skilled practitioner, the use of fixture timing requires a specialized fixture apparatus and is subject to substantial investment of time and labor. For the most part, this process may be described as a trial and error process as the practitioners repeatedly adjust cable lengths to obtain the timed position of the cams.
There arises therefore a need in the art for a simpler less time consuming and burdensome apparatus and method for timing the modern archery bow.